Low calorie bulking agents, such as cellulose, starch, glucans, cereal bran, and hydrocolloids (e.g., xanthan, guar, and alginate), generally are indigestible polymers that can be used in food products. These agents, often referred to as “fiber” or “roughage,” pass through the digestive system for the most part intact, and have been shown to have a number of actual and potential health benefits. As used herein, “fiber” refers to indigestible organic material contained in food, and “hydrocolloid” refers to a material that forms a gel when in contact with water. Fiber and hydrocolloids are capable of absorbing many times their weight in water, causing them to expand greatly in size (often up to a factor of about 20 as compared to the original volume).
The beneficial aspects of fiber in the diet are well recognized. The addition of such indigestible materials to food stimulates the intestine to peristalsis, resulting in increased digestion of accompanying food materials. Due to its effect on digestion, increased consumption of dietary fiber has been linked to decreases in the incidence of gastrointestinal diseases, including bowel cancer.
Additionally, fiber has been suggested as a significant cholesterol-lowering dietary product. Dietary fiber appears to also lower the risk of coronary heart disease through a variety of mechanisms in addition to lowering blood cholesterol, such as attenuating blood triglyceride levels, decreasing hypertension, and normalizing postprandial blood glucose levels. See, e.g., Lupton et al., “Dietary Fiber and Coronary Disease: Does the Evidence Support an Association?,” Curr. Atheroscler. Rep., 5:500-5 (2003). The ability of fiber compounds to relieve hypertension and normalize glucose levels may prove more beneficial to some individuals than its cholesterol-lowering abilities.
Long-term intake of high-dietary fiber has also been shown to have a beneficial effect on glucose tolerance and lipid metabolism, suggesting that it could prove a valuable therapy for treating type 2 diabetes. Li et al., “Long-term Effects of High Dietary Fiber Intake on Glucose Tolerance and Lipid Metabolism in Gk Rats: Comparison among Barley, Rice, and Cornstarch,” Metabolism, 52:1206-10 (2003).
One type of non-fiber compound that appears to lower cholesterol is plant protein (e.g., soy protein). Carroll, “Review of Clinical Studies on Cholesterol-Lowering Response to Soy Protein,” J. Am. Dietetic Assoc. 91:820-827 (1991). Significant decreases in cholesterol levels (in the range of 15 to 20%) have been documented from diets containing primarily soy protein, as compared to control diets containing primarily casein. Meinertz et al., “Soy Protein and Casein in Cholesterol-enriched Diets: Effects on Plasma Lipoproteins in Normolipidemic Subjects,” Am. J. Clin. Nutr., 50:786-793 (1989); Sirtori et al., “Clinical Experience with the Soybean Protein Diet in the Treatment of Hypercholesterolemia,” Am. J. Clin. Nutr., 32:1645-1658 (1979); Sirtori et al., “Soybean-Protein Diet in the Treatment of Type II Hyperlipoproteinemia,” Lancet 275-277 (1977). Nevertheless, the cholesterol-lowering effect of soy protein has not been consistently observed in all subjects, and may be more pronounced in younger subjects and in hyperlipidemic subjects. Meinertz et al., Am. J. Clin. Nutr., 50:786-793 (1989). A combination of dietary fiber and cholesterol-lowering proteins, however, may contribute to significant decreases in LDL cholesterol.
Unfortunately, current food products are unable to take full advantage of many of the above benefits of dietary fiber. It has been suggested that the processing of bran can decrease the cholesterol-lowering benefit ordinarily gained from bran. Kerckhoffs et al., “Cholesterol-Lowering Effect of Beta-glucan from Oat Bran in Mildly Hypercholesterolemic Subjects May Decrease When Beta-glucan Is Incorporated into Bread and Cookies,” Am. J. Clin. Nutr., 78:221-7 (2003).
Consumption of dietary fiber is generally low in the United States and other western countries because of its unsavory texture, mouthfeel, and flavor. This unpalatability of fiber is due, at least in part, by its tendency to absorb water and swell to many times its original size. This ability to absorb water also affects the process dynamics of any food composition containing the fiber. Therefore, it is difficult to add significant amounts of fiber and hydrocolloids to baked products such as cookies, crackers, pasta, dough, extruded snacks, and confections. Furthermore, this capacity to absorb water often makes mastication and digestion of fiber difficult. Absorption of water often also gives such compounds an undesirable texture and consistency. For example, adding uncoated hydrophilic fiber to cookie batter results in a cookie dough that does not spread upon baking, and results in baked products having a dry mouthfeel and an ultimate texture that resembles cake-type products rather than conventional cookie-type products.
Edible coatings for the prevention of water transfer in foods are known in the art. Carbohydrate, lipid, and protein compounds have been used alone and in combination in order to alter the water absorption of various food products, including low calorie bulking agents. Effective coating of fiber to prevent, or significantly reduce water absorption, is very difficult because of the hydrophobic nature and irregular shape of most fibers. Additionally, even slight gaps in the coating can allow rapid water absorption. Despite the fact that the hydrophobic nature of lipids, including fats, oils, and waxes, makes them especially suitable as water impermeable barriers, they have proven to be inadequate barrier layers for fibers because they do not form a continuous barrier surrounding the fibers. Lipid-coated food products generally have holes or gaps in the coating through which water is free to transfer. Carbohydrate coating, although providing continuous coatings, are generally insufficient at preventing water absorption due to their hydrophilic nature. Protein compounds have also proven to be inadequate barriers to water absorption for fibers because of their high zeta potential, which results in incomplete coating of the fibers. Thus, the use of lipid, protein, or a simple mixture thereof has generally been inadequate to fully encapsulate a fiber particle and substantially prevent the absorption of water by the fiber particle.
U.S. Pat. No. 4,915,971 provides an edible film for retarding water transfer among individual components of a multi-component food product. The film is composed of a hydrophilic polymer base layer adjacent to a hydrophobic lipid base layer with its hydrophobic surface presented away from the hydrophilic layer. The film is formed on a non-food supporting surface, and then removed and placed in-between two adjacent components of a food product, such that the hydrophobic lipid layer is oriented toward the food component with higher vapor pressure.
Encapsulation of dietary fiber in a more water-soluble fiber has been described. For example, U.S. Patent Publication 2003/0059458 provides a method for masking of the unappealing sensory properties (e.g., color, flavor, and texture) of carob fiber by encapsulation with a water-soluble dietary fiber.
International Patent Publication WO 00/74501 discloses a particulate fiber composition containing at least one dietary fiber surrounded by an insoluble or low-solubility fiber that will deliver the dietary fiber to a predetermined portion of the digestive tract without dissolution.
U.S. Pat. No. 5,545,414 provides a solid matrix containing protein, fat, and carbohydrate, which has dietary fiber (e.g., guar) encapsulated in zein dispersed therein.
The prior art encapsulated fiber products, although possibly increasing the palatability of the fiber in some applications, do not slow the transfer of water to the extent desired during food processing or digestion. The encapsulated fibers of the present invention have significantly decreased water absorption characteristics. Thus, in addition to increased palatability, the encapsulated fibers of this invention provide improved digestion and result in increased satiety during digestion.